BG Chap 14 - how the soul gets bound up
Material nature consists of three modes – goodness, passion and ignorance. When the unchanging living entity comes in contact with prakṛti, he becomes conditioned by the guṇas, and becomes situated in a body made from the guṇas. The modes bind the jīva with their quality of illusory happiness and distress, which are accepted by the jīva without understanding their true nature. The fault which causes the soul’s conditioned state certainly rests in his own independent desire. Once we come to the material world, we need to assume a false identity, a false ego. False ego, which is like a reflection of our true consciousness within matter, is the covering over the soul first supplied by material nature and is the juncture between our spiritual identity and our material existence. Any ego-identity in which we may imagine ourselves the central figure is acceptable to our perverse consciousness.
Based on that false ego, the elemental ingredients for both subtle and gross material bodies are generated. Based on such bodies, we become controlled by a specific combination of the modes of material nature and “naturally” become attracted to exploiting particular combinations of matter. Thus the soul, constitutionally Kṛṣṇa’s eternal servant—full of bliss, knowledge and eternity—becomes attracted to the material atmosphere and conditioned by it. He is then strictly controlled by the modes of material nature and experiences his self as if it were made of temporary matter.